Kinases are important cellular enzymes that perform essential cellular functions such as regulating cell division and proliferation, and appear to play a decisive role in many disease states such as in disease states that are characterized by uncontrolled proliferation and differentiation of cells. These disease states encompass a variety of cell types and maladies such as cancer, atherosclerosis, and restenosis.
Drugs that target kinases, and especially drugs based on small-molecule chemical compounds that inhibit the activity of kinases, are important medicines that can significantly improve the health, lifespan or quality of life for people throughout the world, including patients suffering from highly debilitating diseases such as cancer. Indeed, the drug “imatinib” (GLEEVEC/GLIVEC; Novartis) is such a drug that inhibits a kinase and is used to successfully treat certain types of cancer including particular types of leukaemia (CML) and gastrointestinal cancer (GIST). Its improved efficacy compared to previous standard treatments for CML, and that it is generally very well tolerated, showing mild side-effects, has lead, among other reasons, for it to have made the cover of TIME magazine where it was described as a “bullet” to combat cancer.
Tyrosine kinases are essential for the propagation of growth factor signal transduction leading to cell cycle progression, cellular proliferation, differentiation, and migration. Tyrosine kinases include cell surface growth factor receptor tyrosine kinases (RTKs) such as FGFr and PDGFr as well as non-receptor tyrosine kinases including c-Src and Lck. Inhibition of these enzymes has been demonstrated to cause antitumor and antiangiogenesis activity (Hamby et al., Pharmacol. Ther, 1999; 82(2-3):169-193).
The molecular mechanisms and signaling pathways that regulate cell proliferation and survival are receiving considerable attention as potential targets for anticancer drug development. Recently, there has been a notable increase in efforts directed at targeting the MAPK pathway, which integrates proliferative signals that are initiated by a wide array of RTKs and G protein-coupled receptors.
The MAPK signal cascade includes a G protein, known as Ras, that works upstream of a core module consisting of three kinases: Raf, MEK1/2 and ERK1/2. In this signal cascade, Raf (a serine/threonine kinase) phosphorylates and thus activates MEK1/2, which in turn ultimately leads to the activation of ERK1/2. Understanding of Raf function in Ras signaling is complicated by the fact that in mammals Raf is encoded by a gene family consisting of three genes (A-raf, B-raf and C-raf (raf-1)) which encode highly conserved 68 to 74 kD proteins (Daum et al., Trends Biochem. Sci. 1994, 19: 474-480) sharing highly conserved amino-terminal regulatory regions and catalytic domains at the carboxyl terminus. Raf proteins are normally cytosolic but are recruited to the plasma membrane by the small G-protein Ras, with this being an essential step for Raf activation by growth factors, cytokines, and hormones. Raf activation at the membrane occurs through a highly complex process involving conformation changes, binding to other proteins, binding to lipids, and phosphorylation and dephosphorylation of some residues.
Raf kinases, and particularly B-Raf, have long been considered attractive targets for drug discovery and therapeutic intervention due to their importance as potential checkpoints for cancer-related signal transduction (Tuveson et al., Cancer Cell, 2003, 4: 95-98; Strumberg and Seeber, Onkologie, 2005, 28: 101-107; Beeram et al., J. Clin. Oncol. 2005, 23: 6771-6790).
The importance of the MAPK signalling cascade for the proliferation and survival of tumor cells has recently increased following the discovery of a number of activating mutations of B-Raf in human tumors. Activating Raf mutations have been identified in melanoma, thyroid, colon, and other cancers (Davies et al., Nature, 2002, 417: 949-954; Cohen et al., J. Natl. Cancer Inst., 2003, 95: 625-627; Mercer and Pritchard, Biochim Biophys Acta, 2003, 1653: 25-40; Oliveira et al., Oncogene, 2003, 22: 9192-9196; Pollock et al., Nat. Genet. 2003, 33: 19-20; Domingo et al., Genes Chromosomes Cancer 2004, 39: 138-142; Shih and Kurman, Am. J. Pathol., 2004, 164: 1511-1518). Therefore, in addition to a role in controlling tumors with Ras mutations or activated growth factor receptors, inhibitors of Raf kinases harbor therapeutic potential for tumors carrying a B-Raf oncogene (Sharma et al., Cancer Res. 2005, 65: 2412-2421).
A variety of agents have been discovered to interfere with Raf kinases, including antisense oligonucleotides and small molecules. These inhibitors prevent the expression of Raf protein, block Ras/Raf interaction, or obstruct its kinase activity. Down-regulation of B-Raf activity by siRNA led to decreased tumorigenic potential of 1205 Lu cells (Sharma et al., Cancer Research, 2005, 65: 2412-2421), and by the kinase inhibitor BAY43-9006 (Sorafenib) led to inhibition of the growth of melanoma cells (Panka et al., Cancer Research., 2006, 66: 1611-9). Raf inhibitors that are currently undergoing clinical evaluation show promising signs of anti-cancer efficacy with a very tolerable safety profile. Most advanced is the Raf inhibitor Sorafenib (Nexavar®), which has been in clinical testing for the treatment of metastatic renal cell carcinoma (Ratain et al., Proc. Am. Soc. Clin. Oncol. (ASCO Meeting Abstract), 2004, 23: Abstract 4501; Motzer et al., J. Clin. Oncol. 2006, 24: 16-24) and which was approved in 2007 by the EMEA for the treatment of patients with advanced renal cell carcinoma. (RCC), or kidney cancer, who have failed prior interferon alfa or interleukin-2 based therapy or are considered unsuitable for such therapy, and by the FDA for use in patients with a form of liver cancer known as hepatocellular carcinoma, when the cancer is inoperable.
The family of mitogen-activated protein (MAP) kinases are proline-directed serine/threonine kinases that activate their substrates by dual phosphorylation. The kinases are activated by a variety of signals including nutritional and osmotic stress, UV light, growth factors, endotoxin and inflammatory cytokines. One group of MAP kinases is the p38 kinase group that includes various isoforms (e.g., p38a, p39ss, p38 or p388).
The p38 kinases are responsible for phosphorylating and activating transcription factors as well as other kinases, and are activated by physical and chemical stress, proinflammatory cytokines, and bacterial lipopolysaccharides.
More importantly, the products of the p38 phosphorylation have been shown to mediate the production of inflammatory cytokines, including TNF, IL-1, and cyclooxygenase-2. These cytokines have been implicated in numerous disease states and conditions. For example, TNF-α is a cytokine produced primarily by activated monocytes and macrophages. Its excessive or unregulated production has been implicated as playing a causative role in the pathogenesis of rheumatoid arthritis. More recently, inhibition of TNF production has been shown to have broad application in the treatment of inflammation, inflammatory bowel disease, multiple sclerosis and asthma.
TNF has also been implicated in viral infections, such as HIV, influenza virus, and herpes virus including herpes simplex virus type-1 (HSV-1), herpes simplex virus type-2 (HSV-2), cytomegalovirus (CMV), varicella-zoster virus (VZV), Epstein Barr virus, human herpes virus-6 (HHV-6), human herpes virus-7(HHV-7), human herpes virus-8 (HHV-8), pseudorabies and rhiriotracheitis, among others.
Similarly, IL-1 is produced by activated monocytes and macrophages, and plays a role in many pathophysiological responses including rheumatoid arthritis, fever and reduction of bone resorption.
Additionally, p38 has been implicated in stroke, Alzheimer's disease, osteoarthritis, lung injury, septic shock, angiogenesis, dermatitis, psoriasis and atopic dermatitis, see, e.g., J. Exp. Opin. Ther. Patents, (2000) 10(1).
The inhibition of the above-mentioned cytokines by inhibition of the p38 kinase can be of benefit in controlling, reducing and/or alleviating one or more of these disease states.
Despite the progress that has been made, the search continues for low molecular weight kinase inhibitor compounds, especially compounds that inhibit Raf kinases, that are useful for treating a wide variety of diseases, including cancer, tumors and other proliferative disorders or diseases including restenosis, angiogenesis, diabetic retinopathy, psoriasis, surgical adhesions, macular degeneration, and atherosclerosis, or other disorders or diseases mentioned above. Thus, a strong need exists to provide compositions, pharmaceuticals and/or medicaments with kinase inhibitory activity, particularly inhibitory activity against one or more Raf kinases, or with anti-proliferative activity against cells such as tumour cells. Such compositions, pharmaceuticals and/or medicaments may possess not only such activity, but may also exert tolerable, acceptable or diminished side effects in comparison to other anti-proliferative agents. Furthermore, the spectrum of tumors or other diseases responsive to treatment with such compositions, pharmaceuticals and/or medicaments may be broad. The active ingredients of such compositions, pharmaceuticals and/or medicaments may be suitable in the mentioned indication as single agent, and/or in combination therapy, be it in connection with other therapeutic agents, with radiation, with operative/surgical procedures, heat treatment or any other treatment known in the mentioned indications.
It is known that specific classes of pyrido[2,3-d]pyrimidines, substituted in a specific manner, have pharmacologically useful properties. In particular, specific derivatives of pyrido[2,3-d]pyrimidin-7-one are known to possess anti-proliferative activity. These compounds however are structurally dissimilar from the compounds of the present invention.
WO 96/34867 discloses 2-substituted and 2,8-disubstituted 6-aryl-pyrido[2,3-d]pyrimidin -7-ones and 7-imino derivatives thereof, that are shown to inhibit tyrosine kinases and to have certain activity in tumor models (see also U.S. Pat. No. 5,620,981 and U.S. Pat. No. 5,733,914). WO 01/55147 discloses 5,6-disubstituted 2,7-diamino-pyrido[2,3-d]pyrimidines having similar activities. WO 01/70741 discloses substituted 2-amino-5-(alkyl,aryl)-pyrido[2,3-d]pyrimidin-7-ones, that are shown to have Cdk inhibitor activity. WO 02/18380 discloses 8-unsubstituted and 8-substituted 2-amino-6-aryl-pyrido[2,3-d]pyrimidin-7-ones, that are shown to inhibit protein kinases, including p38. WO 02/18380 and WO 03/088972 disclose 2,4,8-trisubstituted pyrido[2,3-d]pyrimidin-7-ones, that are shown to inhibit kinases and are thus are able to inhibit the production of various cytokines. WO 02/064594 discloses 8-unsubstituted and 8-substituted 2-amino-6-(amino,oxy)-pyrido [2,3-d]pyrimidin-7-ones and 7-imino derivatives thereof, that are shown to inhibit protein kinases, including p38. WO 03/062236 discloses 2-(pyrid-2-yl)amino-pyrido[2,3-d]pyrimidin-7-ones (optionally substituted at positions 5, 6 and/or 8), that are shown to be potent inhibitors of Cdk 4. WO 03/066630 discloses 6-(monocyclyl)-pyrido[2,3-d]pyrimidin-7-ones (optionally substituted at positions 2, 4 and/or 5), that are shown to be inhibitors of Cdks, and that showed activity in an ischemic stroke model. WO 2004/063195 discloses derivatives of 2-amino-8-methyl-6-phenyl-pyrido[2,3-d]pyrimidin-7-one that are shown to inhibit Bcr-Abl kinase.
In particular, PCT publication WO 03/062236 discloses 2-(pyrid-2-yl)amino-pyrido[2,3-d]pyrimidin-7-ones and 2-(pyrid-2-yl)amino-dihydropyrido[2,3-d]pyrimidin-7-ones (optionally substituted at positions 5, 6 and/or 8), as potent and selective inhibitors of Cdk 4 (and Cdk 6), and compares certain such compounds to their C2-phenylamino analogues, as disclosed in WO 98/33798 and WO 01/70741. The generic Markush structure disclosed and claimed in WO 03/062236 includes, amongst other suggested substituents at the nitrogen in position 8, a generically described substituent being “C1 to C8 alkoxy”. WO 07/136,465 discloses certain 6-(alkoxy-aminocarbonylphenyl)-pyrido[2,3-d]pyrimidin-7-ones for treating diseases and discorders associated with abnormal kinase activities. The generic Markush structure disclosed and claimed in WO 07/136,465 includes, amongst other suggested substituents at the nitrogen in position 8, a generically described substituent —O—R7, with —R7 including “C1-8 alkyl”.